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  Partner: UNT Libraries
 Department: Department of Chemistry
 Collection: UNT Theses and Dissertations
An NMR Study of Trimethylsilylmethyllithium Aggregates and Mixed Trimethylsilylmethyllithium/Lithium trimethylsilylmethoxide Aggregates

An NMR Study of Trimethylsilylmethyllithium Aggregates and Mixed Trimethylsilylmethyllithium/Lithium trimethylsilylmethoxide Aggregates

Access: Use of this item is restricted to the UNT Community.
Date: December 2004
Creator: Medley, Marilyn S.
Description: An NMR spectroscopy study of trimethylsilylmethyllilthium, TMSM-Li, indicates that TMSM-Li exists as two different aggregates in cyclopentane solution. Using previously reported colligative properties of TMSM-Li in different solutions in connection with new 13C and 6Li NMR data collected in this study, aggregation states were assigned as octamer and hexamer. Low temperature 13C and 6Li NMR peak intensities indicated an equilibrium exists between the two aggregates that shifts toward the octamer as the temperature decreases. ΔH was calculated to be 5.23 + 0.15 kcal/mol and ΔS was calculated to be 17.9 + 0.6 eu for the hexamer/octamer equilibrium system. Samples of TMSM-Li were mixed with TMSM-OH in attempts to form mixed alkyllithium/lithium alkoxide aggregates. 13C NMR data for these mixtures gave inconclusive results whether or not these compounds formed, which is different from other primary alkyllithium compounds studied in the past. A study of neopentyllithium, NpLi, indicates only one aggregate in solution with the aggregation state unknown using low temperature 13C NMR spectroscopy.
Contributing Partner: UNT Libraries
A Chemical Analysis of the Important Soils of Dimmit County, Texas

A Chemical Analysis of the Important Soils of Dimmit County, Texas

Date: August 1938
Creator: Meek, William
Description: The purpose of this study is to collect sample soils from uncontaminated horizon (by digging completely through the soil profile or strata) and provide a chemical analysis of the important soils of Dimmit county, Texas.
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The Polarographic Study of P-nitroacetophenone

The Polarographic Study of P-nitroacetophenone

Date: 1952
Creator: Messick, Bobby G.
Description: The purpose of this investigation is to study the polarographic characteristics of p-nitroacetophenone.
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Interaction of learning approach with concept integration and achievement in a large guided inquiry organic class.

Interaction of learning approach with concept integration and achievement in a large guided inquiry organic class.

Date: August 2009
Creator: Mewhinney, Christina
Description: A study was conducted to investigate the relationship of students' concept integration and achievement with time spent within a topic and across related topics in a large first semester guided inquiry organic chemistry class. Achievement was based on evidence of algorithmic problem solving; and concept integration was based on demonstrated performance explaining, applying, and relating concepts to each other. Twelve individual assessments were made of both variables over three related topics - acid/base, nucleophilic substitution and electrophilic addition reactions. Measurements included written, free response and ordered multiple answer questions using a classroom response system. Results demonstrated that students can solve problems without conceptual understanding. A second study was conducted to compare the students' learning approach at the beginning and end of the course. Students were scored on their preferences for a deep, strategic, or surface approach to learning based on their responses to a pre and post survey. Results suggest that students significantly decreased their preference for a surface approach during the semester. Analysis of the data collected was performed to determine the relationship between students' learning approach and their concept integration and achievement in this class. Results show a correlation between a deep approach and concept integration and a ...
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Acetophenone Derivatives; N-Diphenylmethyl and N-Fluorenyl Piperidines

Acetophenone Derivatives; N-Diphenylmethyl and N-Fluorenyl Piperidines

Date: 1949
Creator: Middleton, William J.
Description: This thesis is a study of α-(4-aminophenylsulfonyl)-acetophenone derivatives; n-diphenylmethyl and n-fluorenyl piperidines.
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The Preparation of Pyridinium Derivatives by the Knoevenagel Condensation

The Preparation of Pyridinium Derivatives by the Knoevenagel Condensation

Date: May 1955
Creator: Miller, Eugene James
Description: An attempt is made in the work described in this paper to extend the series started by Hall and Platas by means of a Knoevenagel condensation between 3-hydroxy-1,4-naphtho-quinone-2-(4-methylpyridinium) anhydride and various aromatic aldehydes giving rise to a series of unsaturated substituents on the four position of the pyridine ring.
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Reducing the Computational Cost of Ab Initio Methods

Reducing the Computational Cost of Ab Initio Methods

Date: August 2008
Creator: Mintz, Benjamin
Description: In recent years, advances in computer technology combined with new ab initio computational methods have allowed for dramatic improvement in the prediction of energetic properties. Unfortunately, even with these advances, the extensive computational cost, in terms of computer time, memory, and disk space of the sophisticated methods required to achieve chemical accuracy - defined as 1 kcal/mol from reliable experimental data effectively - limits the size of molecules [i.e. less than 10-15 non-hydrogen atoms] that can be studied. Several schemes were explored to help reduce the computational cost while still maintaining chemical accuracy. Specifically, a study was performed to assess the accuracy of ccCA to compute atomization energies, ionization potentials, electron affinities, proton affinities, and enthalpies of formation for third-row (Ga-Kr) containing molecules. Next, truncation of the correlation consistent basis sets for the hydrogen atom was examined as a possible means to reduce the computational cost of ab initio methods. It was determined that energetic properties could be extrapolated to the complete basis set (CBS) limit utilizing a series of truncated hydrogen basis sets that was within 1 kcal/mol of the extrapolation of the full correlation consistent basis sets. Basis set truncation for the hydrogen atom was then applied to ...
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Predicting Chemical and Biochemical Properties Using the Abraham General Solvation Model

Predicting Chemical and Biochemical Properties Using the Abraham General Solvation Model

Date: May 2009
Creator: Mintz, Christina
Description: Several studies were done to illustrate the versatillity of the Abraham model in mathematically describing the various solute-solvent interactions found in a wide range of different chemical and biological systems. The first study focused on using the solvation model to construct mathematical correlations describing the minimum inhibitory concentration of organic compounds for growth inhibition towards the three bacterial strains Porphyromonas gingivalis, Selenomonas artemidis, and Streptococcus sobrinus. The next several studies expand the practicallity of the Abraham model by predicting free energies of partition in chemical systems. The free energy studies expand the use of the Abraham model to other temperatures and properties by developing correlations for the enthalpies of solvation of gaseous solutes of various compounds dissolved in water, 1-octanol, hexane, heptane, hexadecane, cyclohexane, benzene, toluene, carbon tetrachloride, chloroform, methanol, ethanol, 1-butanol, propylene carbonate, dimethyl sulfoxide, 1,2-dichloroethane, N,N-dimethylformamide, tert-butanol, dibutyl ether, ethyl acetate, acetonitrile, and acetone. Also, a generic equation for linear alkanes is created for use when individual datasets are small. The prediction of enthalpies of solvation is furthered by modifying the Abraham model so that experimental data measured at different temperatures can be included into a single correlation expression. The temperature dependence is directly included in the model ...
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Kinetics and Thermochemistry of Halogenated Species

Kinetics and Thermochemistry of Halogenated Species

Date: May 1997
Creator: Misra, Ashutosh
Description: Gas phase kinetics and thermochemistry of several halogenated species relevant to atmospheric, combustion and plasma chemistry were studied using experimental and ab initio theoretical techniques.
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The Chemical Analysis of the Tennessee Green Pod Pole Bean

The Chemical Analysis of the Tennessee Green Pod Pole Bean

Date: 1941
Creator: Mitchell, O. R.
Description: The object of this paper is to compare the Tennessee green pod pole bean with other beans as to chemical composition and food value.
Contributing Partner: UNT Libraries